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USGS2008

Geology of the Carnegie museum dinosaur quarry site of Diplodocus carnegii, Sheep Creek, Wyoming

The holotype of Diplodocus carnegii Hatcher, 1901, consists of a partial skeleton (CM 84) that was recovered, along with a second partial skeleton of the same species (CM 94), from the upper 10 m of the Talking Rock facies of the Brushy Basin Member of the Morrison Formation exposed along Bone Quarry Draw, a tributary of Sheep Creek in Albany County, Wyoming. A composite measured section of the stratigraphic interval exposed adjacent to the quarry indicates that the Brushy Basin Member in this area is a stacked succession of lithofacies consisting of hackly, greenish gray, calcareous mudstone and greenish brown, dense, fine-grained limestone. The more erosion resistant limestone layers can be traced over many hundreds of meters. Thus, these strata do not appear to represent a highly localized deposit such as a stream channel, oxbow lake, or backwater pond. The Sheep Creek succession is interpreted as representing a clastic-dominated lake where high turbidity and sediment influx produced deposition of calcareous mudstone. During drier periods the lake's turbidity decreased and limestone and dolomite precipitation replaced mud deposition. Microkarsting at the top of some limestone/ dolomite layers suggests subaerial deposition may have prevailed during these dry episodes. The quarry of D. carnegii was excavated within the top strata of one of the numerous intervals of hackly, greenish gray, calcareous mudstone that represent an ephemeral freshwater lake. The quarry strata are directly overlain by 0.3 m of dolomite-capped limestone that was deposited shortly after interment of D. carnegii in the lake mudstones. The close vertical proximity of the overlying limestone to the skeleton's stratigraphic: level suggests that the animal's carcass may have been buried beneath the drying lake deposits during a period of decreased rainfall.

Annals of Carnegie Museum↗

USGS2012

Distributional records of shrews (Mammalia, Soricomorpha, Soricidae) from Northern Central America with the first record of Sorex from Honduras

Short term surveys for small mammals in Guatemala and Honduras during 1992–2009 provided important new records for 12 taxa of shrews from 24 localities. These locality records expand the known geographic distributions for five species and for the genus Sorex Linnaeus, 1758: the geographic range of Cryptotis goodwini Jackson, 1933, now includes the Sierra de las Minas, Guatemala, and several isolated highlands in western Honduras; the known distribution of Cryptotis mayensis (Merriam, 1901) is increased with the first definite modern record for this shrew from Guatemala; Cryptotis merriami Choate, 1970 , is now known to occur in the Sierra de las Minas and the Sierra del Merendón, Guatemala, as well as the isolated Sierra de Omoa and Montana de La Muralla in Honduras, and its documented elevational range (600–1720 m) is expanded; records of Sorex veraepacis Alston, 1877, expand the known distribution of this species to include the Sierra de Yalijux, Guatemala; and discovery of Sorex salvini Merriam, 1897, at Celaque, Honduras (1825–3110 m), represents a considerable extension of the geographic range of the species, and it is the first record of the genus Sorex from Honduras. In addition, the first record of potential syntopy among C. goodwini, C merriami, and Cryptotis orophilus (J.A. Allen, 1895), is reported at an elevation of 1430 m in the Sierra de Celaque, Honduras. Information associated with these records contributes substantially to knowledge of habitat use, elevational distributions, reproductive patterns, diet, and parasites of the species encountered. General patterns include the first evidence that Neotropical species of soricids have smaller litters than their temperate congeners.

Central America↗

USGS1997

A note on the trilobite genus Dixiphopyge

Recovery of the first nearly complete thoracopygon of the trilobite genus Dixiphopyge Brezinski from the Chouteau Formation of central Missouri aids in evaluating the paleoecology and taxonomic affinities of this genus. Dixiphopyge is an isopygous trilobite, suboval in outline, and possessing nine thoracic segments. At the apex of each axial ring is a hollow tubercle that may represent the base of a short spine. Dixiphopyge inhabited muddy biostrome environments. In an enrolled position Dixiphopyge is interpreted to have looked somewhat like a porcupine with its spines radiating outward, presumably to inhibit its consumption by predators. Previous subfamily assignment of Dixiphopyge in the Otarioninae with Cyphaspis and Namuropyge may have been incorrect, because the latter two genera possess broad preglabellar fields and are micropygous.

Annals of Carnegie Museum↗

USGS1998

Significance of nearshore trace-fossil assemblages of the cambro-ordovician deadwood formation and Aladdin Sandstone, South Dakota

The Cambro-Ordovician Deadwood Formation and Aladdin Sandstone represent intertidal and subtidal, nearshore deposystems that contain few well-preserved body fossils, but contain abundant trace fossils. The present study uses the much neglected trace-fossil fauna to describe the diverse paleoenvironments represented in the Deadwood-Aladdin deposystems, and to better understand the environmental conditions that controlled benthic life in the Early Paleozoic. The Deadwood-Aladdin ichnotaxa can be separated into three distinct assemblages based on the changing sedimentologic and hydrodynamic conditions that existed across the Cambro-Ordovician shelf. Trace-fossil assemblages and corresponding lithofacies characteristics indicate that the Deadwood-Aladdin deposystems formed within an intertidal-flat and subtidal-shelf environment. Based on the distribution and numbers of preserved ichnotaxa, the intertidal flat can be subdivided further into an ecologically stressful inner sand-flat environment, and a more normal marine outer sand-flat environment, both of which belong to a mixed, Skolithos-Cruziana softground ichnofacies. The inner sand flat is characterized by low diversity, low numbers, and a general lack of complexly constructed ichnotaxa. Trace fossils common to both assemblages tend to be smaller in the inner flat compared to the outer sand flat. Taphonomic effects, such as substrate type and sediment heterogeneity, also aid in differentiating between the inner and outer sand-flat assemblages. The subtidal shelf environment is categorized in the Cruziana Ichnofacies. Ichnological evidence of periodic tempestite deposition and hardground development within this subtidal regime is manifested by high diversity and low abundance of ichnogenera.

Annals of Carnegie Museum↗

USGS2000

New Lower Mississippian Trilobites from the Chouteau Group of Missouri

Reexamination of existing trilobite collections from the Kinderhookian (Lower Mississippian) Chouteau Group of central and northeastern Missouri indicates that two different suites of trilobites are present in these two areas of the state. Moreover, the study of these collections has led to the erection of a new genus and four new species. The new genus, Ameropiltonia, is based on a new species, A. lauradanae. This genus and species is commonly confused with Breviphillipsia sampsoni (Vogdes). Elliptophillipsia rotundus, n. sp., differs from the type species of this genus by possessing a rounded frontal lobe to the glabella. The other new species, Perexigupyge chouteauensis and Richterella hessleri, are present in the Compton Limestone of Marion and Ralls counties of northeastern Missouri. Variations in trilobite species found in the Compton Limestone of central Missouri and the northeastern part of the state are interpreted to be environmentally related. It appears that the lime mudstone and wackestone lithologies characteristic of the Compton Limestone of central Missouri were deposited in a low-energy, subtidal shelf setting. The lime packstone-grainstone strata of northeastern Missouri are interpreted to have formed as a tidal sand belt on the eastern margin of the Burlington shelf.

Annals of Carnegie Museum↗

USGS2023

Two new species of small-eared shrews of the Genus Cryptotis Pomel, 1848, from the Colombian Andes (Mammalia: Eulipotyphla: Soricidae)

Shrews (Mammalia: Eulipotyphla: Soricidae) reach the southern limit of their New World distribution in the Andes and eastern coastal highlands of northern South America. South of Honduras, the family is represented only by species of the genus Cryptotis Pomel, 1848. In South America, soricids are restricted to moist, high-elevation environments above 1000 m, and their distribution appears to be discontinuous. Study of specimens from a previous gap in the known geographical range of shrews in the Central Cordillera of southwestern Colombia reveals the presence of two unique populations that are distinguishable from each other and their congeners by a combination of morphological and morphometrical characters. They are described herein as, Cryptotis huttereri, n. sp. and Cryptotis andinus, n. sp. Both species are members of the Cryptotis thomasi group, one of five species groups of small-eared shrews defined partly on the basis of postcranial morphology and potential locomotor behavior. Although species in the C. thomasi group share similar postcranial architecture, as exemplified by the morphology of the forelimb, the group appears to be polyphyletic, implying convergence in locomotor behavior, possibly one uniquely adapted for Andean-type montane habitats. Recognition of C. huttereri and C. andinus brings the total number of known South American soricids to 19 species, with 11 species occurring in Colombia. Of those, seven species are endemic to that country.

Annals of the Carnegie Museum↗